US2008151998A1PendingUtilityA1
Method and Apparatus for Providing Rate Control for Panel-Based Real Time Video Encoder
Est. expiryDec 21, 2026(~0.4 yrs left)· nominal 20-yr term from priority
Inventors:Yong He
H04N 19/177H04N 19/147H04N 19/172H04N 19/115H04N 19/61H04N 19/124H04N 19/14H04N 19/152
47
PatentIndex Score
0
Cited by
0
References
0
Claims
Abstract
A method and apparatus is provided for panel-based rate control in an MPEG encoder. In one embodiment, the method begins by estimating a complexity measure of pictures in a GOP and calculating a GOP bit budget for the GOP. Portions of the GOP bit budget are assigned to the pictures in the GOP based at least in part on the estimated complexity measure. A quantization parameter is adjusted for the picture to achieve the assigned portion of bit budget for each picture in the GOP.
Claims
exact text as granted — not AI-modified1 . At least one computer-readable medium encoded with instructions which, when executed by a processor, performs a method comprising:
estimating a complexity measure of pictures in a GOP; calculating a GOP bit budget for the GOP; assigning portions of the GOP bit budget to the pictures in the GOP based at least in part on the estimated complexity measure; and adjusting a quantization parameter for the picture to achieve the assigned portion of bit budget for each picture in the GOP.
2 . The computer-readable medium of claim 1 further comprising preventing encoder and decoder buffers from overflowing or underflowing before encoding a picture in the GOP.
3 . The computer-readable medium of claim 2 wherein preventing of the buffers from overflowing or underflowing includes estimating a current buffer level.
4 . The computer-readable medium of claim 2 wherein preventing of the buffers from overflowing or underflowing includes calculating a number of bits in the pictures that do not overflow or underflow the buffers using an end-to-end buffer delay.
5 . The computer-readable medium of claim 1 wherein calculating the GOP bit budget includes assuming a film mode of the GOP is the same as a film mode of a previously processed picture.
6 . The computer-readable medium of claim 1 wherein the quantization parameter is adjusted using a nominal activity measure.
7 . The computer-readable medium of claim 1 wherein estimating the compexity measure includes determining the complexity measure of P and B pictures in accordance with the expression
C
pic_type
=
W
⊗
C
pic_type
*
∑
W
,
where C* is the complexity of a previously encoded picture of the same type and W is a sequence of weightings W={ 1 , 2 , 2 , 4 }.
8 . The computer-readable medium of claim 1 wherein calculating the GOP bit budget includes assigning a nominal number of bits to the GOP in accordance with the expression
R
GOP
=
f
film_factor
×
N
GOP
×
bit_rate
pic_rate
,
f
film_factor
=
{
1.0
video
mode
1.25
1080
I
film
mode
2.5
720
P
film
mode
}
9 . The computer-readable medium of claim 1 wherein assigning portions of the GOP bit budget to pictures of type I, P and B includes using the expressions
R
frame_target
=
K
pic_type
C
pic_type
R
Gop_remaining
K
I
n
frame_I
C
frame_I
+
K
P
n
frame_P
C
frame_P
+
K
B
n
frame_B
C
frame_B
for
frame
pictures and
R
field_target
=
K
pic_type
C
pic_type
R
Gop_remaining
K
I
n
field_I
C
fieldI
+
K
P
(
n
field
0
_P
C
field
0
_P
+
n
field
1
_P
C
field
1
_P
)
+
K
B
n
field_B
C
field_B
for field pictures.
10 . The computer-readable medium of claim 1 wherein after assigning a portion of the GOP bit budget to a picture includes updating a remaining number of bits in the GOP bit budget in accordance with the expression R GOP — remaining =R GOP — remaining −R target . where R target is the frame/field target bits of the current picture.
11 . The computer-readable medium of claim 1 wherein the step of adjusting the quantization parameter includes determining three virtual buffer fullness, one for each picture of type I, P and B at time t in accordance with
d
pic_type
(
t
)
=
d
pic_type
(
0
)
+
α
×
B
pic_type
(
t
)
-
∑
i
=
0
MB
i
nbs
i
total_nbs
R
pic_target
where d pic — type (0) is an initial virtual buffer fullness at the beginning of a picture of I, P or B type and d pic — type (t) is the final virtual buffer fullness of the picture, B pic — type (t) is a number of bins generated from coded MBs up to time t, α is the ratio of a total number of actual bits and the total number of bins for a previously-coded picture of the same coding type, and (nbs[i]) is a nominal buffer size for a MB.
12 . The computer-readable medium of claim 11 wherein the nominal buffer size (nbs[i]) for a MB is calculated in accordance with
nbs
i
=
α
×
Intra_Act
[
i
]
+
Intra_Act
_Ave
α
×
Intra_Act
_Ave
+
Intra_Act
[
i
]
=
α
×
(
Intra_Act
[
i
]
Intra_Act
_Ave
)
+
1
α
+
(
Intra_Act
[
i
]
Intra_Act
_Ave
)
where the average of the total intra activity (Intra_Act_Ave) is the total activity (Total_Intra_Act) divided by the number of macroblocks in the picture.
13 . A video encoder, comprising:
a panel distributor for partitioning pictures in a video stream into a plurality of panels; a plurality of video panel picture encoders (PPEs) each for compressing one of the plurality of panels; a packet processor receiving each of the compressed panels and generating therefrom transport packets that include compressed bitstreams; a rate controller for adjusting at least one encoder parameter to achieve a target bitrate for the compressed bitstreams; wherein the rate controller is configured to: estimate a complexity measure of pictures in a GOP in the video stream; calculate a GOP bit budget for the GOP; assign portions of the GOP bit budget to the pictures in the GOP based at least in part on the estimated complexity measure; and adjust the encoder parameter for the picture to achieve the assigned portion of bit budget for each picture in the GOP.
14 . The video encoder of claim 13 wherein the rate controller is further configured to prevent encoder and decoder buffers from overflowing or underflowing before encoding a picture in the GOP.
15 . The video encoder of claim 14 wherein the rate controller is further configured to prevent the buffers from overflowing or underflowing by estimating a current buffer level.
16 . The video encoder of claim 14 wherein the rate controller is further configured to prevent the buffers from overflowing or underflowing by calculating a number of bits in the pictures that do not overflow or underflow the buffers using an end-to-end buffer delay.
17 . The video encoder of claim 13 wherein the rate controller is further configured to calculate the GOP bit budget by assuming that a film mode of the GOP is the same as a film mode of a previously processed picture.
18 . The video encoder of claim 13 wherein the encoder parameter includes a quantization parameter and the rate controller is further configured to adjust the quantization parameter using a nominal activity measure.
19 . The video encoder of claim 13 wherein the rate controller is further configured to estimate the compexity measure by determining the complexity measure of P and B pictures in accordance with the expression
C
pic_type
=
W
⊗
C
pic_type
*
∑
W
,
where C* is the complexity of a previously encoded picture of the same type and W is a sequence of weightings W={ 1 , 2 , 2 , 4 }.
20 . The video encoder of claim 13 wherein the encoder parameter includes a quantization parameter and the rate controller is further configured to adjust the quantization parameter by determining three virtual buffer fullness, one for each picture of type I, P and B at time t in accordance with
d
pic_type
(
t
)
=
d
pic_type
(
0
)
+
α
×
B
pic_type
(
t
)
-
∑
i
=
0
MB
i
nbs
i
total_nbs
R
pic_target
where d pic — type (0) is an initial virtual buffer fullness at the beginning of a picture of I, P or B type and d pic — type (t) is the final virtual buffer fullness of the picture, B pic — type (t) is a number of bins generated from coded MBs up to time t, α is the ratio of a total number of actual bits and the total number of bins for a previously-coded picture of the same coding type, and (nbs[i]) is a nominal buffer size for a MB.Join the waitlist — get patent alerts
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